Andy Burnham's claim that he has been the subject of "malicious briefing" is one of the first signs of mutual antagonism in what has otherwise been a comradely Labour leadership contest. As the former health secretary explains, he "nearly fell out of his chair" when he read that he was set to make an early exit from the contest to avoid the humiliation of finishing in fifth place.

His campaign team is refusing to point the finger at anyone, but Ed Balls is widely thought to be the culprit. Balls, who has run a strong campaign, has done much to try to shed his reputation as a hostile briefer. The former schools secretary has even seized the opportunity to moralise by accusing the Miliband brothers of briefing against each other.

He said: "Between the brothers there has been a little bit of off-the-record briefing going on. Hopefully, the two of them will say to their supporters to stop it. It is pretty unedifying." He added: "There will be no off-the-record briefings from anybody involved with me."

Should Balls be up to his old tricks again it will do him no favours. He has impressed in recent weeks with his Question Time demolition of Vince Cable, his fierce protest against the rise in VAT (a tax increase he has long warned about) and his exposure of Michael Gove's school building errors.

Let's hope that Burnham's warning shot prevents any further briefing in a contest that could turn very nasty indeed.

UPDATE: This from my colleague Mehdi Hasan - Ed Balls responds to the latest "smear" claim

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